using it right now...some impressions.
-quality is not good. Sounds a lot like 96kpbs, not even 128.
-It asked me to download WMA (the codec) before instalation, so its not mp3, but is WMA format, so its probably 64kbps, perhaps even 48.
-finding similar music...still there and better than ever. It makes it great to find more bands from a similar genre, sub genre, similar artists, related artists, similar bands etc. Two thumbs way up on that part.
-not enough music it seems, as gopunk said, no obscure ones

. They didnt have anything from Therion, Tristania, Treatre of Tragedy or any other such bands. They didnt have anything from Tool either. Two thumbs way down.
-UI is nice, nothing spectacular, nothing awful.
I've only used it for about 1/2hr, but conclusion is this: If they sign up more labels and offer high quality downloads, this could be a great service. Depending on how much you can stream (or how much unlimited costs), this will be the best way to find and listen to new music without a doubt(not in age, but as in music you have not heard before). In the short time, I head music from 4 bands which I had heard good things about. Very nice
This might be the frist for-pay service to make a break.